helps needed

[Nigel Goodwin]

wow... now these i don really understand...

so how am i suppose to tune the NE567???

What do you think the 22K pot on pin 5 is for?.

 

[chinsoon]

well, i tried many ways, including tuning the variable resistor... and the result is still the same...

thanks to Audioguru and RON H who taught me how to modify it, i managed to pull up the output voltage of the NE567 from 1mV to 3mV ( i donno how it happened)... but still not enough to trigger the relay...

 

[Nigel Goodwin]

thanks to Audioguru and RadioRon who taught me how to modify it, i managed to pull up the output voltage of the NE567 from 1mV to 3mV ( i donno how it happened)... but still not enough to trigger the relay...

That's not helping at all - the output should be a switched signal, either 0V or the supply voltage - if you've had your 567's connected as you showed originally, then they are probably both blown?.

 

[chinsoon]

I have everything connected as shown in the figure. I even changed the NE567 to make sure that the problem is not the IC. but the results remains the same.

That is why i hope to find out there is there any other factors that will affect my output... my problem now is that i can see difference of the output of the NE567 before and after i turning on the transmitter, but the difference just isnt enough to trigger the relay.

Any suggestion how to overcome this? or any idea why is this happening?

 

[audioguru]

Your first schematic has a missing resistor in series with the base of the BC307 transistor that causes the output transistor of the NE567 to blow up and maybe also the base of the BC307 to blow up.
The output of the NE567 is the collector of an NPN transistor that is trying to go to ground but the base of the BC307 is holding it at 0.7V less than the positive supply with a very high current.
The BC307 is also missing a resistor to turn it off.

The BC307 might not be required since the output of the NE567 can drive a 100mA load (that is connected to the positive supply) directly.

The circuit is missing a diode across the coil of the relay to arrest the inductive voltage spike produced when the relay turns off.

The capacitor at the output of the NE567 is not recommended.

 

[bananasiong]

This device operates at 27 MHz right? What's the purpose of the tank circuit of the transmitter (39 pF and L2)? And is the modulatind signal coming from the 555 timer which is 584 Hz?

 

[chinsoon]

This device operates at 27 MHz right? What's the purpose of the tank circuit of the transmitter (39 pF and L2)? And is the modulatind signal coming from the 555 timer which is 584 Hz?

actually that was my question as well... still do not understand why is it there... but it seems like its a path for the RF current to radiate...

yes... 27MHz.. and the frequency of the 555 timer is 580HZ...

 

[chinsoon]

Your first schematic has a missing resistor in series with the base of the BC307 transistor that causes the output transistor of the NE567 to blow up and maybe also the base of the BC307 to blow up.
The output of the NE567 is the collector of an NPN transistor that is trying to go to ground but the base of the BC307 is holding it at 0.7V less than the positive supply with a very high current.
The BC307 is also missing a resistor to turn it off.

The BC307 might not be required since the output of the NE567 can drive a 100mA load (that is connected to the positive supply) directly.

The circuit is missing a diode across the coil of the relay to arrest the inductive voltage spike produced when the relay turns off.

The capacitor at the output of the NE567 is not recommended.

Talking about that, i changed the transistors and also the NE567... but i still cant get the output... and i took away the capacitor like what u said, and follow the diagram that you posted that day....

is there any other possibility that cause this?

 

[audioguru]

When the NE567 has an input signal of 20mV at its input that it is tuned to, then its output will go to ground. It says in the datasheet.

 

[bananasiong]

Pin 8 og the NE567 is the collector of a NPN transistor, u need to pull up to Vcc via the coil of the relay and with diode protection. When it receives signal, the transistor sill conduct and switch the relay, when there is no signal, pin 8 should be measured as high as Vcc and the relay is not switched.

What I don't understand is the RF part, what is the purpose of they crystal? Then how about the tank?

 

[audioguru]

The crystal oscillator in the transmitter makes a very accurate frequency but it is a rough square-wave full of harmonics that cause interference. The tank filters out the harmonics.

 

[bananasiong]

and take only the fundamental, 27 MHz? The tank will oscillate itself, won't it?

 

[audioguru]

The tank is in an RF amplifier, it is not part of the crystal oscillator.

 

[chinsoon]

hi there...

after so many time trying i still cant get the circuit working. I've tried many ways such as using op amp, connect the relay directly to the NE567 and so on.

But i found many problems. First, the voltage to my ZN414. It is stated on the datasheet that the voltage to the ZN414 is only 1.1 to 1.3V. but when i measured the voltage, the input voltage is about 8V. and the 8V comes from the IFT. any idea why?

and when i turn on the transmitter, with my receiver off, there is also responds, which is the tone burst waveform. and i tried to amplify the voltage using op amp but the input voltage is somehow BIGGER than the output voltage.

Any idea why?

 

[Nigel Goodwin]

You've connected the transformer the wrong way, and probably blown the chip?.

 

[chinsoon]

You've connected the transformer the wrong way, and probably blown the chip?.

Em.. there is such possibility. I mean i cant find any information or the way to connect the IFT. So i did it based on the circuit diagram. It shows that the input side has 2 pins and the output side has 3 (something like a center tap) so i followed accordingly. is that wrong?

By the way. is there any possibility that this circuit will not work. As in i got this from a website that did not state that it is tested. So my lecturer is questioning whether is this the issue or not.

 

[Nigel Goodwin]

Em.. there is such possibility. I mean i cant find any information or the way to connect the IFT. So i did it based on the circuit diagram. It shows that the input side has 2 pins and the output side has 3 (something like a center tap) so i followed accordingly. is that wrong?

Why not check where the wondings connect with a meter?.

By the way. is there any possibility that this circuit will not work. As in i got this from a website that did not state that it is tested. So my lecturer is questioning whether is this the issue or not.

It looks to be a simple enough circuit?, assuming your lecturer knows anything about electronics he should know it looks pretty viable.

 

[bananasiong]

Hi,
For the LM567 PLL, is it the demodulated signal goes into the input pin?
Then RC at pin 5 and 6 tune to the modulating frequency by 1/(1.1RC)?
The maximum input signal to pin 3 is only 200 mV?
When the input frequency and the tuned frequency are match, the transistor at the output is turned on right?
I'm not quite sure about that even I've read the datasheet.

Thanks.

 

[bananasiong]

Hi,
According to the datasheet, the maximum frequency, fo is 500 kHz, but the minimum is not stated. I've tried with 5 kHz, but it doesn't work as expected. The output seems to be oscillating. When I change the fo to 200 kHz, then it works. Pin 8 goes low when the variable resistor is tuned to match the input frequency.
From the datasheet as well, the maximum input voltage is 200 mVrms. Is it going to be damaged if the input signal is higher? Up to 2 Vpp?

 

[chinsoon]

Hi,
According to the datasheet, the maximum frequency, fo is 500 kHz, but the minimum is not stated. I've tried with 5 kHz, but it doesn't work as expected. The output seems to be oscillating. When I change the fo to 200 kHz, then it works. Pin 8 goes low when the variable resistor is tuned to match the input frequency.
From the datasheet as well, the maximum input voltage is 200 mVrms. Is it going to be damaged if the input signal is higher? Up to 2 Vpp?

Well, I am not using the LM567. I used the NE567, where some of the specs are different.

for the range of the frequency within its detection, maybe you can refer to the datasheet of the NE567. I am not sure whether is that what you are looking for, but there definitely states that the range of frequency is 0.01Hz to 500KHz

**broken link removed**

but the 2Vpp, generally i think this IC is used in communication circuits only right?( i mean i see that from the list of application on the datasheet.). so i wont be expecting something like 2Vpp to come out from the receiver circuit.(CORRECT ME IF I AM WRONG).

by the way, how did you connect your LM567? that day audioguru has shown me the connection, but i don really understand. the one side of my relay is connected to the +Vcc and the other connected to pin8. it gives me and impression that when the relay is on, the current is flowing into tone decoder through pin8... current flowing into output pin???? very blur on this.